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w116 visco fans

Started by Big_Richard, 19 November 2011, 07:09 PM

Big_Richard

Somehow i got side tracked into watching youtube videos on how to test visco fan clutches on various different cars..

many clips are contradictory.

What's the official method for checking the w116 version at home? the service manual description is a bit useless.

Some people say a loose turning clutch/fan when cold is a bad thing and others say its a good thing. Mines not loose when cold.

driving around my 6.9 the temp stays rock solid at 90c but if stop and go driving it may go up to 100c.

I have an aftermarket aluminium radiator and run a standard clutch fan (with original 30+ year old clutch) but do not run a shroud as it would need to be custom made too. Thats probably half the problem.

(originally i had intended to run the custom radiator with electric fans but that was a colossal fail as there was simply no room)

Possibly the most ambiguous post in the history of the org i know  8)

Big_Richard

Also, Sclass has got me paranoid about finger tight head bolts on m100's.

TJ has advised me against checking the torque of my head bolts as a mind soothing measure as the readings given will be inaccurate unless the bolts are removed one by one, cleaned and then torqued. Can anyone shed more light onto this matter?

Or should I just leave it alone rather than potentially create a massive problem that didn't exist before...

koan

Quote from: Major Tom 6.9 on 19 November 2011, 07:09 PM
What's the official method for checking the w116 version at home? the service manual description is a bit useless.

Is that the bit about running the engine up and listening for the roar?

If it's 30 years old it's probably stuffed. I replaced my clutch because its bearings had a lot of wear and the fan could be tilted on the shaft. I opened the old one up, there wasn't any fluid in it. New clutch was (and is) free when stopped, hardly any resistance to rotation and passes the roar test when running.

Quote from: Major Tom 6.9 on 19 November 2011, 07:14 PM
TJ has advised me against checking the torque of my head bolts as a mind soothing measure as the readings given will be inaccurate unless the bolts are removed one by one, cleaned and then torqued.

TJ's right about cleaning and lubricating bolts if they are going to be reused however...

if the head bolts are dirty or rusted in there's not a problem, unless they came loose then froze up later which I doubt. It's loose ones you're worried about. I don't see anything wrong with setting the torque wrench at say 80% percent of final torque and seeing if any bolts move.

I can tell you on my engine the head bolts were all tight++, every bolt needed lots of heaving to remove.

I'm just wondering if the m100 loose head bolts is a bit of a myth that was born at the eponymous site, it might have happened to somebody once and now its the big fear.

koan
Boogity, Boogity, Boogity, Amen!

Big_Richard

interesting,

So im guessing that at temperature the fan clutch should pretty much be locked up and spinning with the engine at idle.

I dont think i've ever heard the fan roar but it seems to move a decent amount of air.. I might try the rolled up newspaper test too (rolled up newspaper allowed to touch the blades to safely attempt to slow them down) I'm guessing if at temp and the blade is able to be slowed down easily the clutch is stuffed.

koan

#4
Certainly not locked up when stopped either hot of cold, think it depends on centrifugal force generated by rotation.

Do the roar test as per the book.

Or just by a new one, it'll be stuffed if it's original.

koan
Boogity, Boogity, Boogity, Amen!

Big_Richard

Quote from: koan on 19 November 2011, 08:25 PM

Or just by a new one, it'll be stuffed if it's original.

koan

Will do.

KenM

#6
I know for the Toyota Landcruiser it's a service item at 300,000 k's or something like that to renew the grease in the fan clutch. You can buy the appropriate stuff I believe, not sure how it's replaced though. Does this apply with ours or are they permanently sealed?

Squiggle Dog

#7
Maybe this thread will help: http://www.peachparts.com/shopforum/diesel-discussion/195595-refill-viscous-fan-clutch-pictures.html

The bimetallic strip can be removed, the set screw underneath removed, and silicone oil from a Toyota dealer (08816-03001) or silicone axle oil for R/C cars from a store like Hobby Town installed with a syringe. I think the clutches were designed this way so that the fan is not spinning 4,000 RPM with the engine, which causes drag and can damage the plastic fans from the force of the air (so don't try to lock the clutch).
Stop paying for animal cruelty and slaughter. Go vegan! [url="https://challenge22.com/"]https://challenge22.com/[/url]

1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Heated Seats, 350,000+

koan

The 6.9 clutch is a different design. I had the old one sitting around intending to fix the bearings and find some suitable oil but I can't find it after a quick look just know, must have thrown it out. Don't recall there being a bi-metal strip across the front, in fact can't recall a bi-metal strip anywhere but suppose there must have been one. All I can remember is a spring loaded lever that opened and closed a passage way.

Shame I threw it out.

koan
Boogity, Boogity, Boogity, Amen!

Big_Richard

I have 2 litres of silicone oil at home. Never found any use for it at all!

dburkitt

Well Guys, I'm about to take the heads of my 6.9, so I'll be sure to tell you if any of the bolts are finger tight! My brother (the confirmed 126 killer), laid up a 500 SEL (in my back yard, which is the only reason it got fixed in the end as I got bored of looking at it) as he was convinced the head gasket had gone. Turned out to be the viscous fan not doing its bit letting the thing get hot. We swapped it from one out of his previous victims and its still going now, 18 months later. The rest of of the car is royally clucked (or something that rhymes), but that's how he rolls. I have a 560 SEC back at home which he is banned from even thinking about.

The viscous units are fearsomely expensive back the UK...
These go 1 louder, see, up to 11.
Trying to equal things out, I now drive a W123 300D as well.
Oh, and a 560 SEC, oops.
And a Citroen SM, bad Dave.

Big_Richard

I look forward to reading about the tightness or lack there of, of your head bolts.

WGB


s class

Myth or not, the 3 6.9's I've worked on all had loose head bolts.

The worst case was my blue "trusty rusty".  I seriously turned some of the bolts a full turn or more by hand before worrying about the torque wrench.  Maybe I was wrong, but I just put them up to the specified torque, figuring that something close to correct is a lot better than no torque at all.  I must admit I was a bit worried about the possibility of a snapped bolt.

The car has been fine since, done nearly 10 000km and no evidence of head gasket problems. 



[color=blue]'76 6.9 Euro[/color], [color=red]'78 6.9 AMG[/color], '80 280SE, [color=brown]'74 350SE[/color], [color=black]'82 500SEL euro full hydro, '83 500SEL euro full hydro [/color], '81 500SL

Big_Richard

this is the kind of talk that got me so very concerned in the first place  8)

maybe I will try koans suggestion and inspect them to 80% of the book listed torque.